IMP522 Ver la hoja de datos (PDF) - IMP, Inc

Número de pieza

componentes Descripción

Fabricante

IMP522

Dual EL Lamp Driver

IMP, Inc 

IMP522

Application Information

Power Sequencing

To power up the chip, the RSW-OSC pin is connected to VDD through

the external RSW resistor. The voltage on the pin will charge up to

VDD/2. An internal threshold detector circuit monitors the pin

voltage and when it exceeds the threshold range (0.2V to 0.9V) it

powers up the oscillator and internal bias modules. This starts a

delay counter which is one half of the EL oscillator period, after

which power to the high voltage internal modules is applied. The

IMP522 is then operating fully.

To power down the chip, RSW is driven to ground via a switch or

logic gate. When the voltage on the driver side of the resistor falls

below VDD/2, there will be no input bias current into the RSW-OSC

pin. This immediately powers down the internal high-voltage

circuits, which effectively shuts the lamp off. At this point the

oscillator and bias modules still draw quiescent current, but oscil-

lations have ceased. As the RSW-OSC pin voltage falls below 0.1, the

oscillator and bias modules are also fully powered down.

IN (Pulse)

Power Saving Disable Mode

The IMP522 can be powered up and down with RSW-OSC. In

normal operation, this resistor on the RSW-OSC pin is connected to

VDD or another voltage source. To power down (disable) the

IMP522, RSW is connected to ground.

When disabled, the IMP522 quiescent current drops to typically 20nA.

In die form, an extra pin ENABLE is available (contact factory).

Connecting this pad to VDD disables the chip. The ENABLE signal

can be driven by a microcontroller.

Oscillator Frequency Adjustment

The EL lamp drive and PWM boost converter oscillation frequen-

cies can be programmed independently.

The RSW resistor, connected between the RSW-OSC pin and VDD,

determines the Inductor Switching (or PWM-) frequency. For the

recommended nominal resistor value of 910kΩ, the frequency is

61kHz. For other resistor values, the frequency is inversely pro-

portional to the resistor value. Increasing the resistance will lower

the frequency.

ILX

VLX

Figure 1. Driver Waveforms

522_03.eps

The REL resistor, connected between the REL-OSC pin and VDD,

determines the EL lamp drive frequency. For the recommended

nominal resistor value of 2.7MΩ, the frequency is 250Hz. For

other resistor values, the frequency is inversely proportional to

the resistor value: increasing the resistance will lower the fre-

quency.

Oscillator

EL Lamp Drive

Inductor Switch (PWM)

Nominal

Resistor

REL = 2.7MΩ

RSW = 910kΩ

Nominal

Frequency

250Hz

61kHz

522_t03.eps

© 2001 IMP, Inc.

Electroluminescent Lamp Drivers

5

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